I put the capcom theme folder in .emulationstation
referred
DESCNAME=Capcom System I & II
NAME=capcom
PATH=/home/pi/RetroPie/roms/fba
EXTENSION=.zip .ZIP
COMMAND=/home/pi/RetroPie/supplementary/runcommand/runcommand.sh 1 "/home/pi/RetroPie/emulators/pifba/fba2x %ROM%"
# alternatively: COMMAND=/home/pi/RetroPie/supplementary/runcommand/runcommand.sh 1 "/home/pi/RetroPie/emulators/RetroArch/installdir/bin/retroarch -L /home/pi/RetroPie/emulatorcores/fba-libretro/fb_alpha_libretro.so --config /home/pi/RetroPie/configs/all/retroarch.cfg --appendconfig /home/pi/RetroPie/configs/fba/retroarch.cfg %ROM%"
PLATFORMID=23
but the theme doesnt load :(